Several methods are known to make products or articles from fibrous materials. One of these methods comprises the step of forming an article or a preform therefor, from pulp fiber with the use of a mold, which is also called pulp molding. Pulp molding is attracting increased attention from the point of view of resource saving and environmental protection by recycling, since various materials such as packaging materials can be made from used paper products.
In an example of the pulp molding process, a raw pulp suspension is prepared by dispersing pulp fibers in water to obtain a suspension and adding a thermosetting resin to the suspension to impregnate the pulp fibers with the thermosetting resin. Next, the method comprises a step in which the mold is contacted with the raw pulp suspension and the pressure is reduced inside the mold (metal mold). Since the mold is made so as to admit the passage of water from the raw pulp suspension, the pulp fibers accumulate over the surface of the mold. In this way a pulp fiber preform is formed which is then dried and subjected to pressure and/or elevated temperature to obtain the molded pulp product.
FIG. 1 is a schematic sectional view of a mold used in pulp molding. In FIG. 1, a mold 50 is a so-called draining mold. The mold 50 comprises a mold main body 58 in the shape of a hollow rectangular parallelepiped with a projection, which consists of three division molds (58A to 58C) each made from cast metal, and a lid 53 for closing an opening 52 of the mold main body 58.
The mold main body 58 (division molds 58A to 58C) has a plurality of suction holes 56 which provide communication between the inside space 51 and the outside of the mold. The outside surface of the mold main body 58 (division molds 58A to 58C) is covered with wire cloth 57A to 57C. The diameter of the suction holes 56 is within a range of about 2 to 15 mm. The size of the openings of the wire cloth 57A to 57C (size of the particles which can pass through the wire cloths) is within a range of about 0.1 to 1 mm.
A suction device 54 is connected to the mold 58 with a suction pipe 55. By operating the suction device 54, a reduced pressure is produced in the inside space 51 of the mold 58.
FIG. 2 illustrates the process step in which the mold 50 is contacted with the pulp suspension to make a pulp fiber preform. In FIG. 2, a raw pulp suspension 60, in which pulp fibers of a few millimeters in length are dispersed in water, is held in a raw material vat 59.
The main body 58 of the mold 50 is put in the raw pulp suspension 60. The suction device 54 is then operated to reduce the pressure of the inside space 51 of the mold main body 58. Because of this reduced pressure in the inside space 51, a suction force which attracts the pulp fibers is generated on the outside surface (the surface covered with the wire cloth 57A to 57C) of the mold main body 58. Being pulled beg this force, the pulp fibers accumulate over the outside surface of the mold main body 58, and thereby the preform of the product is obtained. This preform is then subjected to several process steps such as drying and curing under pressure. Thereby, a molded product is obtained, which has a shape corresponding to that of the mold 50.
However, since the mold 50 shown in FIG. 1 needs a wire mesh stretching operation to cover the outside surface of the mold main body 58 (division molds 58A to 58C) with the wire cloths 57A to 57C, it cannot be manufactured efficiently.
The wire mesh stretching operation is very difficult when stretching wire mesh along the surface of a mold which has complicated projections end recessions. Further, when the mold consists of two or more parts, each part needs a separate wire mesh stretching operation, making the wire mesh stretching operations still more complicated and difficult. The wire mesh stretching operation also requires skill in cutting and stretching the wire mesh. Furthermore, it is difficult to quickly meet a request for design change, because remake of the metal mold is required even for a partial change in the shape of the mold.
It is therefore an object of the present invention to manufacture a mold using so-called "laminate fabricating" in which consecutive layers of a resin are irradiated with light to cure the resin (hereinafter referred to as light-irradiating laminate fabricating). Light-irradiating laminate fabricating is the method of forming a three-dimensional object composed of a plurality of firmly united superposed layers of cured resin by repeating the process of selectively irradiating a photocurable resin with light. For this light-irradiating laminate fabricating, photocurable resins such as urethane acrylate, epoxy acrylate, a vinyl ether resin, and an epoxy resin are used.
With the use of light-irradiating laminate fabricating, suction holes can be formed by aligning unexposed parts of all laminated resin layers so that when the uncured resin is removed continuous holes are apparent. It is therefore possible to form suction holes of any diameter by light-irradiating laminate fabricating. For example, suction holes with a diameter smaller than the length of the pulp fibers (1 mm or smaller, for example) can be easily formed. Suction holes with such a small diameter perform both the function of the suction holes 56 of the mold 50 shown in FIG. 1, and that of the wire cloths 57A to 57C. Therefore, the wire mesh stretching operation which requires time and skill becomes unnecessary. Further, even a complicated-shape mold can be made in a single mold without dividing it. It was therefore expected that the manufacture of a mold for pulp molding would become more efficient, and a quicker response to requests for design change would become possible, by use of light-irradiating laminate fabricating.
It is a further object of the present invention to form a water-resistant coating over the surface of the laminate fabricated mold made of cured resin in order to minimize water permeation, improve the durability and extend the useful life of the mold.
It is yet another object of the present invention to provide a fibrous material forming mold for forming products from fibrous materials which can be manufactured efficiently, without a post-care coating step, while still having superior water-resistant properties (durability).
It is yet a further object of the present invention to form a water-resistant laminate Fabricated mold for forming products from fibrous materials wherein the mold comprises a water-resistant, cured resin that minimizes water permeation, improves the durability and extends the useful life of the mold.
It is still a further object of the present invention to provide a water-resistant mold for making products from fibrous materials wherein the mold is formed from a filled resin that is water-resistant.